1. Field of the Invention
The present invention relates to an ion implantation method and a method for manufacturing an SOI wafer.
2. Related Background of the Invention
An SOI (Silicon on Insulator) wafer generally refers to a wafer formed into a layered structure of Si layer/insulating layer/Si substrate by forming a thin insulating layer and a single crystal Si layer near the surface of the Si substrate. In recent years, this SOI wafer has gained attention because the SOI wafer is excellent in that integration and operation speed thereof are higher in comparison with those of a usual bulk Si wafer.
As a method for manufacturing the SOI wafer, a smart-cut method has been known (refer to Japanese Patent Laid-Open Publication 2000-12285 and so on). The smart-cut method is one for fabricating the SOI wafer in the following manner. Specifically, hydrogen ions are implanted into a Si substrate through an insulating layer (SiO2 layer or the like) formed on the surface of the Si substrate, and this substrate is bonded to another Si substrate, followed by partition of the bonded substrates at a portion of such a hydrogen ion implanted layer.
In the foregoing smart-cut method, generally, an arc discharge type plasma source using a hot cathode as an ion source is used in the case of implanting the hydrogen ions into the Si substrate. Because the arc discharge type ion source accelerates electrons to a high energy state between an anode and the cathode to ionize gas, this type of ion source is suitable for efficiently generating single atom ions and multivalent ions. Hence, in this case, hydrogen atom ions (H+) generated from the arc discharge type ion source are implanted into the Si substrate.
In order to easily and securely partition the SOI wafer at the portion of the hydrogen ion implanted layer in a process of manufacturing the SOI wafer, it is extremely important to increase an implantation amount of the hydrogen ions into the Si substrate. Preferably, the implantation amount is 5×1016 ion/cm2 or more. Hence, it is desirable to perform the ion implantation with a high throughput (hydrogen implantation rate into a wafer per unit time).